Identification and characterization of three novel beta 1,3-N-acetylglucosaminyltransferases structurally related to the beta 1,3-galactosyltransferase family

J Biol Chem. 2001 Feb 2;276(5):3498-507. doi: 10.1074/jbc.M004800200. Epub 2000 Oct 19.

Abstract

We have isolated three types of cDNAs encoding novel beta1,3-N-acetylglucosaminyltransferases (designated beta3Gn-T2, -T3, and -T4) from human gastric mucosa and the neuroblastoma cell line SK-N-MC. These enzymes are predicted to be type 2 transmembrane proteins of 397, 372, and 378 amino acids, respectively. They share motifs conserved among members of the beta1,3-galactosyltransferase family and a beta1,3-N-acetylglucosaminyltransferase (designated beta3Gn-T1), but show no structural similarity to another type of beta1,3-N-acetylglucosaminyltransferase (iGnT). Each of the enzymes expressed by insect cells as a secreted protein fused to the FLAG peptide showed beta1,3-N-acetylglucosaminyltransferase activity for type 2 oligosaccharides but not beta1,3-galactosyltransferase activity. These enzymes exhibited different substrate specificity. Transfection of Namalwa KJM-1 cells with beta3Gn-T2, -T3, or -T4 cDNA led to an increase in poly-N-acetyllactosamines recognized by an anti-i-antigen antibody or specific lectins. The expression profiles of these beta3Gn-Ts were different among 35 human tissues. beta3Gn-T2 was ubiquitously expressed, whereas expression of beta3Gn-T3 and -T4 was relatively restricted. beta3Gn-T3 was expressed in colon, jejunum, stomach, esophagus, placenta, and trachea. beta3Gn-T4 was mainly expressed in brain. These results have revealed that several beta1,3-N-acetylglucosaminyltransferases form a family with structural similarity to the beta1,3-galactosyltransferase family. Considering the differences in substrate specificity and distribution, each beta1,3-N-acetylglucosaminyltransferase may play different roles.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line, Transformed
  • Cells, Cultured
  • Galactosyltransferases / chemistry*
  • Humans
  • Insecta
  • Molecular Sequence Data
  • N-Acetylglucosaminyltransferases / classification
  • N-Acetylglucosaminyltransferases / genetics
  • N-Acetylglucosaminyltransferases / isolation & purification*
  • Phylogeny
  • Polysaccharides / metabolism*
  • RNA, Messenger / metabolism
  • Sequence Homology, Amino Acid
  • Tissue Distribution

Substances

  • Polysaccharides
  • RNA, Messenger
  • poly-N-acetyllactosamine
  • Galactosyltransferases
  • N-Acetylglucosaminyltransferases
  • beta--1,3-N-acetylglucosaminyltransferase T4
  • beta-1,3-N--acetylglucosaminyltransferase T3
  • B3GNT2 protein, human

Associated data

  • GENBANK/AB049584
  • GENBANK/AB049585
  • GENBANK/AB049586